Bare Bones Arduino Guide

A Bare Bones Arduino is the simplest Arduino. Why make your own? If you are serious about the Atmega 328P's low power mode and reducing circuit size, you will want to build one. You may also want to ultimately design a product that integrates the Arduino.

Package Contents

Our Bare Bones Arduino Kit contains the following:

1x Atmel AVR 328P microcontroller programmed with Optiboot

1x 16MHz crystal

2x 22pF crystal loading capacitors

2x 100nF decoupling capacitors

1x 10k ohm pullup resistor

1x 330 ohm LED resistor

1x Red LED

Identifying Components

We selected components with differing shapes to help you desern between capacitors. You can also identify the LEDs based on the colored rings on the resistors. Here is how to easily identify all of the components.

Atmel AVR 328P Microcontroller programmed with Optiboot

The microcontroller is pretty easy to identify. It is programmed with Optiboot, which is a much improved Arduino bootloader. But you will want to make sure you find pin 1. This is marked by a little dot indentation in the corner. When you count pins, you will count in a U shaped counter clockwise fashion. Also note that Arduino pin numbers don't actually match up to the physical pin numbers on the chip. Here is a handy guide on what pin does what:

Red LED

We will use the Red LED to run blink in order to verify that our Bare Bones Arduino is working. We will use the LED in conjunction with the 330 ohm resistor to keep it from drawing too much power (and burning up). You can easily identify the polarity of any LED by looking at the lead lengths:

We will orient the positive end towards the microcontroller and the negative end towards our ground line.

16MHz Crystal

The 16MHz crystal oscillator is a metal tin can with two leads. It is not polarized, so it doesn't matter which direction it goes in. This helps generate the clock signal for our Bare Bones Arduino, as we will be using an external clock source. Crystals are also much more accurate than the internal oscillator or an external ceramic resonator. This is important if accurate timing is desired, such as high speed serial communication, or timing critical libraries such as TVOut.

22 pF Loading Capacitors

The 22 pF loading capacitors have square bodies with little wings at the top and do not flare out. They are used in conjunction with the crystal to generate the clock signal. Without the loading capacitors, the crystal will not resonate. These capacitors are square in shape.

100 nF Bypass Capacitor

The 100nF (nanofarad) bypass capacitors are crimped outwards and are labeled as 104. They are used in two different applications in our circuit: First, across power and ground to filter the incoming power and keep things stable. The second application is used in the Ardiuno bootloader to AC couple the DTR line in order to reset the Arduino for programming mode. We will explain more how this works later.

330 Ohm and 10K Ohm Resistor

We will use the 330 Ohm resistor to limit the current that the LED consumes, and the 10K Ohm resistor to pull up the reset line so our microcontroller operates normally. You can identify these two by the different colored bands.